KR200360276Y1 - Electronic Ballast - Google Patents

Abstract

The frequency control function is added to the electronic ballast to sufficiently preheat the filament of the fluorescent lamp with a fixed frequency PWM signal during the preheating period, and when the preheating time elapses, the fluorescent lamp is suddenly reduced while the frequency of the PWM signal is rapidly reduced. If overcurrent flows through the fluorescent lamp, the PWM signal is stopped to prevent damage.

The PWM signal generator generates a PWM signal of a frequency initially set as a resistor for initial frequency setting, and generates a PWM signal whose frequency decreases as power is charged to the frequency adjusting capacitor. A first power supply unit for supplying initial operating power, an inverter unit driven according to a PWM signal, a resonator unit for preheating, igniting and igniting the filament of the fluorescent lamp according to an output signal of the inverter unit, and a current flowing through the fluorescent lamp To generate a PWM signal at a fixed frequency by supplying a second power supply unit supplying operating power to the PWM signal generator and preventing the power supply from being charged to the frequency adjusting capacitor during a predetermined time constant. PWM decreases frequency when power is charged to frequency control capacitor when time constant time elapses That generated the call is composed of a pre-heating time setting.

Description

Electronic Ballast {Electronic Ballast}

The present invention relates to an electronic ballast for lighting a fluorescent lamp by using a PWM (Pulse Width Modulation) integrated device for a half-bridge inverter, and particularly at a fixed frequency regardless of the ignition characteristics of fluorescent lamps having the same rating. The present invention relates to an electronic ballast capable of sufficiently preheating a filament of a fluorescent lamp and then changing it to a switching frequency or less for a short time to improve the shortening of service life due to a difference in ignition characteristics of the fluorescent lamps.

In general, an electronic ballast generates a high frequency signal of a predetermined frequency with a commercial AC power source, and turns on a fluorescent lamp using the generated high frequency signal. The electronic ballast generates a signal of various frequencies to preheat the filament of the fluorescent lamp and to perform the process of ignition and lighting.

Here, the preheating of the filament of the fluorescent lamp is to prevent the blackening phenomenon occurs when the fluorescent lamp is discharged, the process of continuing the lighting of the fluorescent lamp can use the power efficiently by adjusting the brightness of the fluorescent lamp It is to ensure that.

FIG. 1 is a circuit diagram showing a configuration of a conventional electronic ballast using a PWM integrated device dedicated to a half-bridge inverter among the above-described electronic ballasts. As shown in the drawing, a conventional electronic ballast includes a PWM signal generator 100 comprising a PWM integrated device 101, a resistor R1, and capacitors C1 and C2, which generate a PWM signal, and a main power source. A first power supply unit 110 including resistors R2 and R3 and capacitors C3 and C4 for supplying operating power to the PWM signal generator 100 at an initial stage when VDD is supplied; and the PWM signal generator Inverter unit 120 including capacitors C5, resistors R4 and R5, transformers T1, and transistors Q1 and Q2 driven by the PWM signal generated by 100, and the inverter unit 120 The resonator 130 including the fluorescent lamp 131, the capacitor C5, and the primary coil T21 of the transformer T2, which are resonated according to the output signal of the transformer, and both ends of the primary coil T21 of the transformer T2. A secondary coil T22 and a diode D1 of a transformer T2 for supplying stable operating power to the PWM signal generator 100 with voltage. The second power supply unit 140 includes a capacitor C7, a resistor R6, and a constant voltage diode ZD1.

In the conventional electronic ballast configured as described above, when the main power supply VDD is supplied by turning on a power switch (not shown), the supplied main power supply VDD is the resistance R2 of the first power supply unit 110. Charged to the capacitor (C4) through (R3) is supplied as the operating power to the PWM integrated device 101 of the PWM signal generator 100.

In such a state, when the voltage charged in the capacitor C4 rises above the operating voltage of the PWM integrated device 101, the PWM integrated device 101 starts operation to generate a PWM signal having a predetermined frequency, and the generated PWM is generated. In response to the signal, the transistors Q1 and Q2 of the inverter unit 120 alternately operate to generate a driving signal. The resonator unit 130 resonates according to the generated driving signal to preheat and ignite the filament of the fluorescent lamp 131. And lighting continue.

That is, at the initial stage when the PWM integrated device 101 operates, a frequency determined by the resistor R1 connected to the third terminal of the PWM integrated device 101, for example, a frequency of about 75 kHz as shown in FIG. 2. Generates a PWM signal to start preheating of the filament of the fluorescent lamp 131, and the PWM integrated device (up to the switching frequency determined by the time constant of the capacitor C2 connected to the terminal 2 of the PWM integrated device 131) The frequency of the PWM signal gradually decreases linearly with the time constant (from 0 to T2) according to the capacitor C1 connected to the first terminal of the 131, and continuously preheats the filament of the fluorescent lamp 131. The fluorescent lamp 131 is turned on at a frequency that matches the ignition characteristic of 131.

Here, before the fluorescent lamp 131 is turned on, the frequency of the PWM signal and the ignition current flowing through the filament of the fluorescent lamp 131 have an inverse relationship.

That is, the conventional electronic ballast starts the preheating of the filament of the fluorescent lamp 131 with a PWM signal of about 75 Hz at the initial time of turning on the power switch, and the first frequency f1 at which the fluorescent lamp 131 starts to ignite. After preheating the filament of the fluorescent lamp 131 for a preheating time (0 ~ t11) given up to fluorescence within a given time (t1 ~ t2) from the first frequency (f1) to the second frequency (f2) of the ignition period frequency band The lamp 131 is turned on, and after the fluorescent lamp 131 is turned on, the fluorescent lamp 131 is turned on at a frequency corresponding to the ignition characteristics of the fluorescent lamp 131.

However, fluorescent lamps with the same rating also have low ignition current due to differences in characteristics (eg, discharge start current) and characteristics produced by different production lots. That is, the fluorescent lamps that are turned on at high frequencies have a short ignition time and are turned on even when excessive current does not flow into the lamps, thereby ensuring a long service life. However, the fluorescent lamps having a high ignition current, i.e., fluorescent lamps 131 that are turned on at low frequencies, may be used. In this case, too much current flows to preheat the filament, which shortens the service life of the fluorescent lamp 131.

Therefore, the purpose of the present invention is to add a frequency control function to the electronic ballast using the PWM integrated device for the half-bridge inverter, to sufficiently preheat the filament of the fluorescent lamp with a fixed frequency PWM signal during the preheating period, and the preheating time has elapsed. In this case, it is to provide an electronic ballast capable of stably lighting the fluorescent lamp irrespective of the difference in characteristics of the fluorescent lamps having the same rating by lighting the fluorescent lamp while rapidly decreasing the frequency of the PWM signal.

Another object of the present invention is that the fluorescent lamp is defective or the end of the service life of the fluorescent lamp reaches the end of the overcurrent flow, or a power supply of a level higher than the rated voltage, such as three-phase four-wire 380V is applied to the electronic ballast It is to provide an electronic ballast which is not damaged by stopping the generation of the PWM signal when overvoltage and overcurrent are supplied.

The electronic ballast according to the present invention has the purpose of fixing the frequency of the PWM signal for preheating the filament of the fluorescent lamp to a predetermined frequency during the preheating period for preheating the filament of the fluorescent lamp to sufficiently preheat the filament of the fluorescent lamp. Then, the frequency of the PWM signal is drastically reduced during the ignition period, and the fluorescent lamp is turned on.

Therefore, the electronic ballast of the present invention generates a PWM signal with a frequency at which the PWM integrated element is set as an initial frequency setting resistor at the initial time of supplying the main power, and the PWM gradually decreases as the power is charged to the frequency adjusting capacitor. PWM signal generator for generating a signal, a first power supply for supplying initial operating power to the PWM signal generator, an inverter unit driven according to the PWM signal generated by the PWM signal generator, the output signal of the inverter unit Resonates to preheat, ignite and ignite the filament of the fluorescent lamp and maintains lighting, and when the fluorescent lamp is turned on, power is generated by current flowing through the fluorescent lamp to supply operating power to the PWM signal generator. The second power supply unit and the main power supply for a predetermined time constant time at which the main power is supplied. The PWM signal generator generates a PWM signal at a fixed frequency by preventing power from being charged in the water adjusting capacitor, and generates a PWM signal in which the frequency is reduced while the power is charged in the frequency adjusting capacitor when a time constant elapses. It is characterized by consisting of a preheating time setting unit to make.

The preheating time setting unit includes a capacitor and a resistor connected in series to an output terminal of the first power supply unit, a gate of a transistor is connected to a connection point of the capacitor and the resistor, and a drain of the transistor is the frequency adjusting capacitor and the PWM integrated device. It is characterized in that connected to the power supply terminal of.

And a level detector for detecting whether overcurrent or overvoltage is supplied to the fluorescent lamp, and an operation stabilizer for stopping the operation of the PWM integrated device when the level detector detects overcurrent or overvoltage. The level detector includes two resistors connected in series between an output terminal of the second power supply unit and a primary coil of a transformer for supplying power according to a current or voltage supplied to the fluorescent lamp to the second power supply unit. A constant voltage diode configured to output a detection signal having a level corresponding to a current or voltage supplied to the fluorescent lamp at a connection point of two resistors, and wherein the operation stabilization unit is in a conductive state when the level detection unit detects an overcurrent or an overvoltage And, when the constant voltage diode is brought into a conductive state, the PWM integrated device It is composed of the thyristors which block the applied operation power characteristics.

1 is a circuit diagram showing the configuration of a conventional electronic ballast.

2 is a graph showing a frequency change of a PWM signal generated in the PWM integrated device of FIG.

3 is a circuit diagram showing the configuration of the electronic ballast of the present invention.

Figure 4 is a graph showing the frequency change of the PWM signal generated by the PWM integrated device according to the electronic ballast of the present invention.

Explanation of symbols on the main parts of the drawings

100: PWM signal generator 101: PWM integrated device

110: first power supply unit 120: inverter unit

130: resonator 131: fluorescent lamp

140: second power supply unit 200: preheating time setting unit

210: level detector 220: motion stabilization unit

Q10: transistor

Hereinafter, the electronic ballast of the present invention will be described in detail with reference to the accompanying drawings of FIGS. 3 and 4, where the same parts as in the prior art are given the same reference numerals.

3 is a circuit diagram showing the configuration of the electronic ballast of the present invention. As shown therein, a PWM signal generator 100 oscillates to generate a PWM signal, and a first power supply unit which supplies operating power to the PWM signal generator 100 at an initial stage when the main power supply VDD is supplied. 110, the inverter unit 120 driven by the PWM signal generating unit 100 and the preheating filament of the fluorescent lamp 131 while resonating according to the output signal of the inverter unit 120. And a resonator 130 for igniting and continuing lighting, and when the fluorescent lamp 131 is turned on, power is generated by a current flowing through the fluorescent lamp 131 to operate the power supply to the PWM signal generator 100. In the electronic ballast consisting of a second power supply unit 140 for supplying a power supply, the PWM signal generator 100 generates a PWM signal at a constant fixed frequency during a predetermined time constant time initially applied to the main power supply (VDD). Time-lapse time The level of the operating power generated by the preheating time setting unit 200 for generating a PWM signal rapidly decreasing below the switching frequency f2 and the second power supply 140 to which the fluorescent lamp 131 is turned on. To stop the operation by cutting off the power supplied to the PWM signal generator 100 when the level detector 210 detects the power level and the level of the operating power detected by the level detector 210 is equal to or higher than a preset level. It was composed of a stabilization unit 220.

The preheating time setting unit 200, the capacitor (C10) and the resistor (R10) is connected in series to the power supply terminal (terminal 8) of the PWM integrated device 101 of the PWM signal generator 100, The connection point of the capacitor C10 and the resistor R10 is connected to the gate of the transistor Q10 so that the drain of the transistor Q10 is the oscillation frequency variable terminal (terminal 1) and the capacitor C1 of the PWM integrated device 101. Is connected to.

The level detector 210 is a primary of a transformer T2 that provides power to the second power supply 140 when the output terminal of the second power supply 140 and the fluorescent lamp 131 are turned on. The resistors R11 and R12 are connected in series between one terminal of the coil T21 so that the level detection signal is output at the connection point of the resistors R11 and R12.

In the operation stabilization unit 220, an output terminal of the level detector 210 is connected to a resistor of the resistor R14, the capacitor C11, and the constant voltage diode ZD10, and the anode of the constant voltage diode ZD10 is a resistor R13. ) Is connected to the gate of the thyristor (SCR), the anode of the thyristor (SCR) is connected to the power input terminal (terminal 8) of the PWM integrated device 101, and the cathode of the thyristor (SCR) is grounded Is connected to.

When the electronic ballast according to the present invention configured as described above is supplied with a main power supply VDD by turning on a power switch, the supplied main power supply VDD is a capacitor through the resistors R2 and R3 of the first power supply unit 110. When the voltage charged in the C4 and the voltage charged in the capacitor C4 rises above the operating voltage of the PWM integrated device 101, the PWM integrated device 101 starts to generate a PWM signal having a predetermined frequency. do.

Here, the PWM integrated device 101 generates a PWM signal by oscillating at a predetermined frequency set by the resistor R1 at an initial stage of operation, and the frequency of the PWM signal generated as the power is charged to the capacitor C1. Will be lowered.

In this state, the transistors Q1 and Q2 of the inverter unit 120 alternately operate according to the frequency of the PWM signal generated by the PWM integrated device 101 to generate a drive signal, and generate a resonator according to the generated drive signal. As the 130 is resonated, the filament of the fluorescent lamp 131 continues to preheat, ignite, and light.

In this operation, the main power supply VDD is charged in the capacitor C10 of the preheating time setting unit 200 through the resistor R2, the filament of the fluorescent lamp 131, and the resistor R3. Before the capacitor C10 is charged with a predetermined voltage or more, the transistor Q10 is brought into a conductive state at both ends of the resistor R10 so that the transistor Q10 is in a conductive state. Terminal 1 of 101 is connected to the ground through transistor Q10 so that power is not charged in capacitor C1.

Therefore, the PWM integrated device 101 has a predetermined time constant time set by the capacitor C10 and the resistor R10, that is, during the preheating time (0 to t11) of the filament of the fluorescent lamp 131 as shown in FIG. The filament of the fluorescent lamp 131 while continuously generating a PWM signal having a predetermined frequency set to the resistor R1, for example, a frequency of about 63 kHz slightly higher than the first frequency f1 as shown in FIG. Will preheat.

Here, about 63 kHz, which is the frequency of the PWM signal generated by the PWM integrated device 101, may be set to the value of the resistor R1.

In this state, when a predetermined time constant time set by the capacitor C10 and the resistor R10 has elapsed, and the power of the capacitor C10 is charged to a predetermined level or more, the voltage across the resistor R10 is biased by the transistor Q10. It becomes below voltage. Then, contrary to the above, since the transistor Q10 is turned off, power is charged to the capacitor C1, and thus, the frequency of the PWM signal generated by the PWM integrated device 101 is charged to the capacitor C1. It will be lowered according to the power level.

Here, when the capacitance of the capacitor C1 is set low, the power is charged to the capacitor C1 at a high speed, whereby the frequency of the PWM signal generated by the PWM integrated device 101 is fluorescent as shown in FIG. 4. During the ignition periods t11 to t12 of the lamp 131, the lamp 131 is rapidly reduced, thereby igniting the fluorescent lamp 131 in which the filament is sufficiently preheated during the preheating period.

After the time t12 at which charging of the capacitor C1 is completed, the PWM integrated device 101 generates a PWM signal having a frequency lower than the switching frequency f2, and the fluorescent lamp 131 is stably lit. Will be maintained.

Meanwhile, when the fluorescent lamp 131 is turned on, the level detector 210 generates a power according to a current flowing into the fluorescent lamp 130 to supply operating power to the PWM integrated device 101. The voltage between the output terminal of the generator 140 and the primary coil T21 of the transformer T2 for supplying the second power generator 140 with power according to the current flowing through the fluorescent lamp 130 is resistance R11. , Divided into R12 and provided to the operation stabilization unit 220.

In this case, when the fluorescent lamp 131 is normally supplied with the rated current and the rated voltage to the fluorescent lamp 131, the voltage level of the connection point of the resistors R11 and R12 is the constant voltage diode ZD10 of the operation stabilization unit 220. The values of the resistors R11 and R12 and the constant voltage of the constant voltage diode ZD10 are set to be lower than the constant voltage of.

Then, when the rated current and the rated voltage are supplied to the fluorescent lamp 131, since the voltage output from the level detector 210 is lower than the constant voltage of the constant voltage diode ZD10, the constant voltage diode ZD10 does not conduct, thereby While the thyristor SCR continues to be blocked, operation power is continuously supplied to the PWM integrated device 101 to operate normally, and the fluorescent lamp 131 maintains a stable lighting state.

When the fluorescent lamp 131 is defective or the end of the service life of the fluorescent lamp 131 reaches the end, an overcurrent flows or a power supply higher than the rated voltage is applied to the electronic ballast such as a three-phase four-wire type 380V. When the overcurrent and the overvoltage are supplied to the 131, the voltage output from the level detector 210 becomes higher than the constant voltage of the constant voltage diode ZD10 so that the constant voltage diode ZD10 is conducted.

Then, the thyristor (SCR) is triggered to be in a conductive state, the operating power applied to the PWM integrated device 101 flows to the ground through the die thyristor (SCR), so the operating power is not supplied to the PWM integrated device (101). As a result, the PWM signal cannot be generated, and the fluorescent lamp 131 is turned off to prevent damage to the electronic ballast.

On the other hand, while the invention has been shown and described in relation to a specific preferred embodiment, the invention is variously modified without departing from the spirit or field of the invention provided by the following utility model registration claims And one of ordinary skill in the art that the present invention can be changed.

As described above, the present invention generates a PWM signal of a predetermined fixed frequency at the initial stage of turning on the power in an electronic ballast using a PWM integrated device to sufficiently preheat the filament of the fluorescent lamp, and when the preheating of the filament is completed. By turning on the fluorescent lamp while rapidly reducing the PWM signal, the fluorescent lamp life can be assured as much as possible regardless of the distribution of the lighting conditions of the fluorescent lamp due to differences between manufacturers and lots.

In addition, when overvoltage such as 380V of three-phase 4-wire type is supplied to the electronic ballast, or the fluorescent lamp is defective and an overcurrent flows due to the fluorescent lamp, the electronic ballast is detected by stopping the operation of the electronic ballast. Can prevent damage.

Claims (5)

PWM signal generator that generates a PWM signal of the frequency set by the PWM integrated element as the initial frequency setting resistor at the initial time of the main power supply and gradually decreases the frequency as the power is charged to the frequency adjusting capacitor. ; A first power supply unit supplying initial operation power to the PWM signal generator; An inverter unit driven according to the PWM signal generated by the PWM signal generator; A resonator for preheating and igniting the filament of the fluorescent lamp and continuing lighting while resonating according to the output signal of the inverter unit; A second power supply unit generating power with current flowing through the fluorescent lamp and supplying operating power to the PWM signal generator when the fluorescent lamp is turned on; And The PWM signal generator generates a PWM signal at a fixed frequency so that power is not charged in the frequency adjusting capacitor during a predetermined time constant time at which the main power is supplied, and when the time constant time elapses, An electronic ballast consisting of a preheating time setting unit that generates a PWM signal whose frequency decreases as power is charged to a frequency control capacitor. According to claim 1, wherein the preheating time setting unit; A capacitor and a resistor are connected in series to the output terminal of the first power supply, a gate of the transistor is connected to the connection point of the capacitor and the resistor, and a drain of the transistor is connected to the power terminal of the frequency adjusting capacitor and the PWM integrated device. Electronic ballast, characterized in that. The method of claim 1, A level detector for detecting whether an overcurrent or an overvoltage is supplied to the fluorescent lamp; And And an operation stabilizer for stopping the operation of the PWM integrated device when the level detector detects an overcurrent or an overvoltage. The apparatus of claim 3, wherein the level detector; Two resistors are connected in series between an output terminal of the second power supply unit and a primary coil of a transformer providing power to the second power supply unit according to the current or voltage supplied to the fluorescent lamp. And a detection signal having a level corresponding to a current or a voltage supplied to the fluorescent lamp at a connection point. The apparatus of claim 3, wherein the operation stabilization unit; A constant voltage diode in a conducting state when the level detector detects an overcurrent or an overvoltage; And And a thyristor which is triggered when the constant voltage diode is brought into a conductive state and cuts off the operating power applied to the PWM integrated device.